Fluorescence-based analyses and nonisotopic detection systems have become a powerful tool for scientific research and clinical diagnostics for the detection of biomolecules using various assays including, but not limited to, flow cytometry, nucleic acid hybridization, DNA sequencing, nucleic acid amplification, immunoassays, histochemistry, and functional assays involving living cells. Fluorescent semiconductor nanocrystals have found widespread use due to their high fluorescent intensity and the ability of different nanocrystals to be excited by a single light source. It would be desirable to increase the signal from these non-isotopic materials to increase the sensitivity of a variety of assays and analyses utilizing them. It would be advantageous to controllably link numbers of nanocrystals and other small particles into structures for analytical applications that can be used to label a target molecule to be detected.
Mirkin et al, in WO 98/04740 discloses nanoparticles having oligonucleotide attached to them. Methods are disclosed that comprise contacting a nucleic acid with one or more types of nanoparticles having oligonucleotides attached to them. The oligonucleotides are attached to nanoparticles and have sequences complementary to portions of the sequence of the nucleic acid. A detectable change, a color change, is brought about as a result of the hybridization of the oligonucleotides on the nanoparticles to the nucleic acid. The compositions disclosed do not include core/shell semiconductor nanocrystals and use oligonucleotides, specifically complementary oligonucleotides, to form conjugates of the nanoparticles.
Mirkin et al. in U.S. Pat. No. 6,361,944 disclose nanoparticles having oligonucleotides attached to them and uses for the compositions. Again, the disclosure provides oligonucleotides attached to nanoparticles that include core/shell semiconductor nanocrystals and where the oligonucleotide sequences are complementary to portions of the sequence of a nucleic acid to be detected. A detectable change is brought about as a result of the hybridization of the oligonucleotides on the nanoparticles to the nucleic acid. The disclosure purports to illustrate the formation of nanoparticle aggregates, nanomaterials, and nanostructure by combining nanoparticles having complementary oligonucleotides attached to them, the nanoparticles being held together in the aggregates as a result of the hybridization of the complementary oligonucleotides.
Hansen et al. in WO 98/33070 disclose a homogeneous binding assay. The disclosure describes a homogeneous method of measuring chemical binding that relies on resonant, or “amplified”, optical extinction (light scattering plus absorption) from a defined, specific class of colloidal particles where the real term n of the complex refractive index n-ik approaches zero while the imaginary term k approaches 2(1/2). Chemical binding partners are coated onto the particles, which either aggregate or disperse during the binding reaction, causing an optical extinction change at one wavelength that is quantitatively related to the number of single colloidal particles and another at a second wavelength that is quantitatively related to the number of doublet colloidal particles. The disclosure describes the uses of optical extinction to measure the formation of particle dimers (through the appearance of increased extinction at the split resonant wavelength) and the concomitant disappearance of the singlet particles (through the decrease of extinction at the original resonant wavelength).
Bawendi et al. in EP0990903 disclose biological applications of semiconductor nanocrystals. The disclosure describes compositions comprising fluorescent semiconductor nanocrystals associated to a compound, where the nanocrystals have a characteristic spectral emission that is tunable to a desired wavelength by controlling the size of the nanocrystal, and where the emission provides information about a biological state or event.
Barbera-Guillem et al in U.S. Pat. No. 6,261,779 discloses nanocrystals having polynucleotide strands and their use to form dendrimers in a signal amplification system. The disclosure provides compositions and assay kits comprising functionalized nanocrystals having a plurality of polynucleotide strands of known sequence extending from them. The disclosure describes primary dots that are used to operably link to a molecule, and secondary dots comprise a plurality of polynucleotide strands which are complementary to the plurality of polynucleotide strands of the primary dots. The disclosure provides a method for detecting the presence or absence of target molecules in a sample comprising operably linking primary dots to molecules, contacting the complex formed with the sample, contacting the sample with successive additions of secondary dots and primary dots. If a target molecule is present in the sample, the primary dots and secondary dots will form dendrimers that can be detected by fluorescence emission.
Peng et al. U.S. Pat. No. 6,872,249 disclose the synthesis of colloidal nanocrystals. A method of synthesizing colloidal nanocrystals is disclosed using metal oxides or metal salts as a precursor. The metal oxides or metal salts are combined with a ligand and then heated in combination with a coordinating solvent.
Peng et al. U.S. Pat. No. 6,869,545 discloses colloidal nanocrystals with high photoluminescence quantum yields and methods of preparing the same. The disclosure provides compositions containing colloidal nanocrystals with high photoluminescence quantum yields, synthetic methods for the preparation of highly luminescent colloidal nanocrystals, as well as methods to control the photoluminescent properties of colloidal nanocrystals.
Bawendi et al. in U.S. Pat. No. 6,306,610 disclose quantum dot white and colored light emitting diodes. The disclosure describes an electronic device comprising a population of quantum dots embedded in a host matrix and a primary light source which causes the dots to emit secondary light of a selected color, and a method of making such a device. The size distribution of the quantum dots is chosen to allow light of a particular color to be emitted from the structure. The dots can be composed of an undoped semiconductor such as CdSe, and may optionally be overcoated to increase photoluminescence. The host matrix for the device includes isolated dots within the matrix and not defined aggregates of nanocrystals.
U.S. Pub. No. 20040110220 to Mirkin et al. discloses nanoparticles having oligonucleotides attached to them and uses for such coated nanoparticles. The disclosure provides methods of detecting a nucleic acid that comprise contacting the nucleic acid with one or more types of nanoparticles having oligonucleotides attached to them. The disclosure describes a method where oligonucleotides are attached to nanoparticles and have sequences complementary to portions of the sequence of the nucleic acid. A detectable change is brought about as a result of the hybridization of the oligonucleotides on the nanoparticles to the nucleic acid. The disclosure describes methods of synthesizing nanoparticle-oligonucleotide conjugates and methods of using the conjugates. The disclosure describes nanomaterials and nanostructures comprising nanoparticles and methods of nanofabrication utilizing nanoparticles. The disclosure describes a method of separating a selected nucleic acid from other nucleic acids.